When venerable Swiss marque Blancpain introduced its first diving watch in 1953, it was thought that 50 fathoms, or 91 meters, was the deepest a man could dive on SCUBA. Hence the name of their groundbreaking timepiece, arguably the world’s first purpose-built dive watch, the Fifty Fathoms. The watch was revolutionary, with features still common on modern dive watches: a unidirectional rotating bezel, luminous markers and double-sealed crown. As you’d expect, it enjoyed success with various military diving units and cult status among recreational divers before fading into relative obscurity.

Blancpain has since returned to the design roots of the Fifty Fathoms with a tantalizing string of tribute watches, prompting the original diving timepiece to regain its iconic stature. But what do you do for a long overdue second act when you got things so right the first time? Blancpain reinvented the mechanical dive watch, cheekily calling it the X Fathoms ($38,700, limited edition). This one can not only go much deeper but also measure depth down to — you guessed it — 50 fathoms. We break it down for you above.